Devices for breathing air supply for a person with rebreathing system are used in both stationary devices, e.g., anesthesia or ventilation systems, as well as in so-called closed-circuit breathing systems, which are used for rescue operations and for diving. An essential feature of these breathing air supply systems is that the breathing air for supplying a person, especially a patient or a rescue person is circulated in a closed circuit. Part of the CO2 contained in the air exhaled by the person must first be removed from that air within this closed circuit. Furthermore, oxygen is often fed to the air and the temperature of the air is controlled as needed.
If corresponding systems are used for anesthesia devices, CO2 is first removed from the breathing gas exhaled by the patient and the breathing gas is then enriched with oxygen and volatile anesthetic. The utilization of oxygen and volatile anesthetic gases is considerably improved in such a closed process and both the costs are reduced and the environment is protected.
In the prior-art closed-circuit breathing systems with rebreathing system, CO2 is extracted from the breathing gas, as a rule, with so-called breathing lime. Both heat and moisture are generated during the absorption of CO2, because an exothermic reaction is involved here. It is problematic in this connection that the moisture generated during the CO2 absorption may condense on the breathing system components arranged downstream, especially on sensors or valves and thus may lead to impairment of the function or even failures.
To avoid corresponding impairments, electrical or actively regulated heating systems are known, e.g., in the area of anesthesia devices, and these systems prevent the generation of moisture in the breathing system or at least ensure that a corresponding condensation will occur at locations specially intended for this purpose. Such systems often have a comparatively complicated regulation technology, are expensive and have an increased energy consumption.
A carbon dioxide absorber for a closed-circuit breathing system, which has a gas inlet and a gas outlet on the upper side and a condensate collection tank in the lower area, is known from DE 10 2009 007 980 A1. A bed of granular breathing lime, which binds carbon dioxide from a patient during the operation, is located on a perforated plate in the absorber housing. The exhaled gas enters a collection space below the perforated plate via the gas inlet and a duct arranged centrally in the absorber housing and flows from there via the perforated plate and the breathing lime to the gas outlet. Further, a condensate collection tank with a layer of a water-binding substance in the form of a superabsorbing polymer, which substance collects and stores the condensate generated, is located in the lower area of the collection space. The substance thus prevents condensate from flowing back into the breathing lime.
An alternative technical solution for removing moisture from the exhaled air in the closed ventilation circuit, which is based on the use of a room-temperature heat exchanger, is known from DE 10 2006 040 886 A1. A heat exchanger is provided in the closed ventilation circuit for removing water vapor from the ventilation gases to prevent condensation within the closed ventilation circuit. The heat exchanger is arranged in this case downstream of a CO2 absorber and receives the ventilation gases from the CO2 absorber before they flow to the inhalation branch of the closed ventilation circuit. The heat exchanger contains a number of inflow tubes and outflow tubes, which are each open towards a sump, which is detachably fastened to the heat exchanger. The condensate, which condenses from the ventilation gases within the heat exchanger, collects in the sump.
It is common to the prior-art closed-circuit breathing systems that the generation of moisture is not regularly reduced, but the condensation is specifically deflected in the most favorable case into a certain area, which must be maintained and monitored by the user as a consequence of this technical solution.